Internal combustion engine

ABSTRACT

An engine e.g. an internal combustion engine (10) comprises at least one combustion chamber (11-14) in which fuel and air are ignited to produce power, and delivery means (19,16) to deliver the primary fuel to the combustion chamber (11-14), air delivery means (15-17) to provide air to the combustion chamber (11-14) and including a delivery duct (15) through which the air flows prior to entering the combustion chamber (11-14), an apparatus (25) to provide a secondary fuel to the combustion chamber, the secondary fuel being different from the primary fuel, the apparatus (25) comprising a housing (26) having therein: 
     a) a chamber (30) in which the secondary fuel is stored in liquid state, and, 
     (b) a heating device (35) into which liquid fuel may flow from the chamber (30), the heating device (35) being adapted to heat the secondary fuel sufficiently to cause at least vaporisation and preferably cracking thereof, 
     and the housing (26) having outlet means (46) from which the secondary fuel can pass in vapour state and there being passage means along which the secondary fuel flows towards the combustion chamber (11-14).

DESCRIPTION OF INVENTION

This invention relates to an engine and more particularly, but notexclusively, to an internal combustion engine for a vehicle such as amotor car or lorry, although the invention may be applied to a statickind of internal combustion engine or another kind of engine if desired.

In GB Patent 2169654 there is disclosed an internal combustion engine inwhich a secondary fuel comprising mineral oil is vaporised and fed tothe engine to improve the efficiency of combustion within the engine.The apparatus described comprises a tank which contains the mineral oil,and a separate heating device to which the secondary fuel flows undergravity or is pumped, and a trap where the vaporised mineral oil isretained until it is fed to the internal combustion engine.

It has been found that such a construction presents problems due to thespace taken up by the tank and separate heating device, as well as thetime taken to convert a conventional internal combustion engine toutilise the secondary fuel.

According to one aspect of the invention we provide an engine comprisingat least one combustion chamber in which fuel and air are ignited toproduce power, delivery means to deliver the primary fuel to thecombustion chamber, air delivery means to provide air to the combustionchamber and including delivery duct means through which the air flowsprior to entering the combustion chamber, an apparatus to provide asecondary fuel to the combustion chamber, the secondary fuel beingdifferent from the primary fuel, characterised in that the apparatuswhich provides the secondary fuel to the combustion chamber comprises ahousing having therein:

(a) a chamber in which the secondary fuel is stored in liquid state,and,

(b) a heating device into which liquid fuel may flow from the chamber,the heating device being adapted to heat the secondary fuel sufficientlyto cause at least vaporisation thereof,

and the housing having outlet means from which the secondary fuel canpass in vapour state and there being passage means along which thesecondary fuel flows towards the combustion chamber.

It has been found that an arrangement in accordance with the inventionovercomes the technical and commercial problems with the prior artarrangements exemplified above.

The secondary fuel is preferably fed into the duct means through whichthe combustion air passes prior to entering the combustion chamber suchthat the combustion air and secondary fuel together pass into thecombustion chamber.

The invention may be applied to an internal combustion engine in which adriven part is moved as a result of the combustion of the air and fuel,either of the spark ignition or diesel type. Where the engine is of thespark ignition type, the combustion air may be mixed with fuel upstreamof the duct in a carburettor, or the primary fuel is injected directlyinto the combustion chamber.

Where the engine has a carburettor, the secondary fuel may pass with theprimary fuel and the combustion air mixture into the combustion chamber.

Alternatively, where the primary fuel is injected into the combustionchamber, the secondary fuel may be injected with or separately from theprimary fuel into the combustion chamber.

Where the secondary fuel is fed into the duct means through which thecombustion air passes prior to entering the combustion chamber, the airin the duct means may if desired, be at least partially pre-compressed,or may be at ambient pressure. In the former case, the secondary fuelwould need to be positively injected into the duct means; in the lattercase, the secondary fuel may be injected into the duct means, or inducedtherein by the flow of air, as desired.

In the latter case, the quantity of secondary fuel which is induced intothe duct means, may be metered.

It has been found that where the secondary fuel comprises a suitablehigh octane hydrocarbon fuel, such as for example a mineral oil, e.g.paraffin which contains a high proportion of branched chain isomers, theefficiency of the engine is increased significantly compared with aconventional engine. In turn, this increase in efficiency reducessignificantly the production of harmful exhaust emissions such as smoke,particulates, carbon monoxide, hydrocarbons and oxides of nitrogen.Where applied to an internal combustion engine and combined with acatalytic converter for example, or other means for cleansing theexhaust emissions from the engine, the emissions which pass into theatmosphere eventually can be rendered virtually harmless.

The housing may be of any desired configuration but preferably issubstantially cylindrical, comprising a cylindrical side wall and topand bottom closure plates. Thus the longitudinal axis of the cylindermay extend substantially upright in use, or generally horizontal asdesired.

Means may be provided to limit the degree to which the chamber can befilled with liquid secondary fuel such that a space is provided abovethe liquid into which the secondary fuel in vapour state may pass fromthe heating device prior to passing out of the housing via the outletmeans.

The heating device may be of any desired configuration but preferably iscontained within a sheath which may be generally cylindrical. The sheathmay be provided anywhere convenient within the housing as desired, butpreferably is generally concentric therewith.

The heating device may comprise a heat exchanger into which the liquidsecondary fuel passes from the chamber of the housing, and the heatingdevice may include a heating means to provide heat to the heat exchangersuch that the secondary fuel is heated therein.

The heat exchanger is preferably insulated from the liquid secondaryfuel in the chamber. For example mineral and/or ceramic insulation maybe provided between the sheath and the heat exchanger. If desired, priorto passing into the heat exchanger, the secondary fuel, in liquid state,may pass into a jacket surrounding the heating device such that the fuelis preheated.

The heat exchanger may conveniently comprise a coil made for example ofstainless steel or brass, and where the heating means is upright, thesecondary fuel may enter the coil towards a bottom end of the heatingmeans, and may flow upwardly into the coil as it is heated.

In one arrangement, the heating means comprises an electrical heatingelement, for example contained within a tube, and the coil or other heatexchanger may be provided around the tube.

Temperature sensing means comprising for example a thermostat,thermistor, thermocouple or positive resistance thermocouple (PRT)sensor may be provided to sense the temperature to which the secondaryfuel is heated by the heating means, and to provide a signal to a remotecontrol means which controls the heating effect of the heating means.

In another arrangement, instead of an electrical heating means, anotherkind of heating means may be provided. For example, heat generated bythe internal combustion engine may be harnessed to heat the secondaryfuel. It is envisaged that hot exhaust gases may be fed to the heatingdevice and the heat thereof exchanged in the heat exchanger with thesecondary fuel.

In this latter case, preferably a control means is provided whichincludes a valve means to control the amount of the exhaust gases andhence the heat thereof generated by the internal combustion engine,which is fed to the heating device.

In each case, the control means may be adapted to maintain thetemperature to which the secondary fluid is heated, to a temperature inthe range 310° C. to 450° C. but in any event preferably below 600° C.,thus to crack the hydrocarbon based secondary fuel.

A typical housing of a secondary fuel apparatus of an engine inaccordance with the invention preferably is, externally, less than 6inches in length, and preferably less than 3 inches in diameter, andthus has a maximum volume of about 0.7 of a liter.

Preferably, for a larger engine which requires a greater quantity ofsecondary fuel than can be provided by a secondary fuel apparatus ofsuch small dimensions, rather than scaling up the dimensions of theapparatus, preferably a plurality of smaller dimensioned such apparatusmay be provided each feeding secondary fuel in vapour state to thecombustion chamber or chambers of the engine, e.g. via a common vapourreservoir.

Alternatively, for a large capacity engine, a plurality of smalldimensioned secondary fuel apparatus may each contribute individually,secondary fuel in vapour state, to the engine.

The invention will now be described with reference to the accompanyingdrawings in which:

FIG. 1 is a schematic illustration of an internal combustion engine inaccordance with the invention,

FIG. 2 is a side cross sectional view through a secondary fuel apparatusfor use in the engine of FIG. 1,

FIG. 3 is a plan view of the apparatus of FIG. 2,

FIG. 4 is a sectional view on the arrows IV--IV of FIG. 2.

FIG. 5 is a cross-sectional view of an alternate embodiment of asecondary fuel apparatus for use in the engine of FIG. 1, and

FIG. 6 is a cross-sectional view of another alternate embodiment of asecondary fuel apparatus for use in the engine of FIG. 1.

Referring first to FIG. 1, an internal combustion engine 10 comprises inthis example, four combustion chambers 11,12,13 and 14, each containinga piston which reciprocates in its respective combustion chamber inresponse to the ignition of a fuel/air mixture under compression.

Air is fed into each of the respective combustion chambers 11-14 via anair inlet manifold 15 to which air is supplied via in this example, acarburetter 16 to which in turn air is supplied from the atmosphere viaan air filter 17.

A primary fuel is stored in a tank 18 and is pumped via a pump 19 to thecarburetter 16 as is well known in the art, and the fuel and air aremixed together in the carburetter 16 such that an air fuel vapourmixture is fed to the inlet manifold 15.

In an alternative arrangement, where a carburetter 16 is not provided,fuel from the tank 18 may be injected directly into each of thecombustion chambers 11-14 when appropriate, via suitable injectorsindicated at 21,22,23 and 24 respectively.

In accordance with the present invention, a secondary fuel apparatus 25is provided to supply secondary fuel to the combustion chambers 11-14,and enhance the efficiency of combustion of the primary fuel therein.

Referring now to FIGS. 2 to 4, the secondary fuel apparatus 25 comprisesa housing 26 having a generally cylindrical side wall 27 a top plate 28and a bottom plate 29, the housing 26 in use being arranged in asubstantially upright orientation. If desired, the apparatus 25 mayalternatively be arranged such that the housing is in a generallyhorizontal orientation, or any other suitable orientation.

The housing 26 thus provides within it, a chamber 30 which containssecondary fuel. Secondary fuel may be introduced into the chamber 30either via a fill hole 31 which extends through the top plate 28 of theapparatus, or via a side fill hole 32.

Arranged concentrically within the housing 26, there is provided aheating device 35 which comprises an outer sheath 36 conveniently ofstainless steel or the like, and containing within it a heating means37. In the example shown in FIG. 2, the heating means 37 comprises anelectrical resistance heating element, electrical leads for the elementbeing indicated at 39 and 40, extending out of the housing 26 through anopening in the bottom plate 29, and extending to a remote control means33.

Surrounding the heating element 37, there is a heat exchanger 42comprising a coil made of stainless steel or brass.

Secondary fuel may pass from the chamber 30 into the coil 42 at aposition 43 towards the bottom end of the heating means 35, by gravity,and flows upwardly through the coil 42 as it is heated by the heatingmeans 37. The fuel is at least vaporised and passes out of the coil 42at position 44 into a space 45 provided above the maximum fill level ofthe secondary fuel in the chamber 30. Because it is possible that someunvaporised fuel can pass out of the coil 42 at position 44, a splashplate 49 is provided so that any such liquid fuel will impinge upon theplate 49 and fall downwardly back into the chamber 30. The secondaryfuel in vapour state however can pass out of the housing 26 via anoutlet 46 which is connected via suitable pipework or tubing (not shown)to the inlet manifold 15 of the internal combustion engine 12. In apreferred arrangement, the housing 26 is in thermal contact with a hotpart of the engine, such as an exhaust manifold thereof, so that thesecondary fuel in chamber 30, is warmed.

Between the sheath 36 and the coil 42 of the heating means 35, mineraland/or ceramic insulation is provided as indicated at 47 to restrict theamount of heat loss from the coil 42 to the liquid secondary fuelcontained within chamber 30. The insulation 47, where ceramic, maycomprise a cast block, or ceramic beads for examples.

Alternatively, or additionally, as is illustrated in FIG. 6, a jacket 38may be provided around coil 42, e.g. by means of a second concentricsheath, and the secondary fuel may be constrained to flow in liquidstate into the jacket prior to passing into coil 42, such that thesecondary fuel is preheated in the jacket.

In each case, between the coil 42 and the sheath 36, there is provided atemperature sensing means 48 comprising in this example a thermocouple,electrical leads indicated at 50 extending from the thermocouple 48,through a suitable opening in the bottom plate 29 of the housing 26 tothe remote control means 33.

In use, as the engine 10 runs, electrical current is supplied to theheating element 37 of the heating device 35 such that secondary fuel inthe coil 42 is heated to a temperature of above 310° C., and below 600°C., preferably below 450° C. The secondary fuel in the coil 42 is thuscracked so that vapours containing methane, ethylene, and propylene,along with other hydrocarbon gases such as butane and butalene etc. areproduced. One suitable kind of secondary fuel is paraffin, althoughanother mineral oil or even a processed vegetable oil or a mixture ofthese may be used if desired. In each case, the secondary fuel in thechamber 30 is different from the primary fuel in the tank 18, and ispreferably of a greater octane rating.

Thus the efficiency with which the primary fuel is burned in thecombustion chambers 11-14, is enhanced and this has the effect ofreducing the production of harmful exhaust emissions.

In the arrangement shown in FIGS. 2-4, the apparatus 25 has an overalllength of about 4 inches, and a diameter of about 2 inches, such thatthe maximum capacity of the chamber 30 is less than a quarter of aliter. Hence the apparatus 25 does not take up any significant space inthe engine compartment of a motor vehicle for example in which theinternal combustion engine 10 may be provided.

By providing sufficiently efficient insulation 47 between the sheath 36and the heat exchanger 42 and ensuring that the coil 42 is made of asufficiently high conductivity metal, the power consumption of theelectrical heating element 37 can be kept to an absolute minimum. Intrials, the continuous electrical load has been measured at only 1.5amps.

If desired, the apparatus may be controlled so as to operate onlyintermittently. This works because it has been found that use of theapparatus 25 described to produce secondary fuel in vapour state whichis fed into the engine has a residual effect i.e. the benefits mentionedabove continue for a time even when no secondary fuel is being fed intothe combustion chamber or chambers.

Various modifications are possible without departing from the scope ofthe invention. For example, the housing 26 need not be of thecylindrical configuration described, and nor need the heating device 35be provided within the cylindrical sheath 36 concentrically within thehousing 26. A housing 26 and a heating device 35 of alternateconfigurations may be provided. For example, the heating device 35 maybe provided adjacent the cylindrical side wall 27 of the housing 26.

It is envisaged that the housing 26 may be made as an integral part ofan engine casting, or of another part of the engine which becomes hot inuse, so that the secondary fuel in chamber 30 is warmed in the chamber30.

Although the heat exchanger through which the secondary fuel flows whileit is heated is described above as a coil 42, a heat exchanger ofanother suitable configuration may instead be provided.

If desired, secondary fuel in liquid state may be stored externally ofthe chamber 30 and fed to the chamber 30 by a pump or under gravity suchthat the fill level of the secondary fuel in chamber 30 is maintainedconstant.

Instead of a thermocouple 48, any other temperature sensing means suchas a thermostat, thermistor or PRT sensor could be provided.

Instead of a heating element 37, the heat generated by the internalcombustion engine 10 may be harnessed to heat the secondary fuel in theheating device 35. For example, a proportion of the hot exhaust gasesproduced by the engine may be fed to the heating device 35 such that theheat thereof is given up to the secondary fuel within the coil 42 orother heat exchanger.

In each case, preferably a control means 33 is provided to control thetemperature to which the secondary fuel is heated.

Where the heating means comprises an electrical heating element 37, thecontrol means 33 may include a relay or other circuit interrupter, whichresponds to the temperature sensed by the temperature sensor 48, to cutoff the supply of electrical current to the heating element 37 when thetemperature sensor 48 senses a maximum temperature.

Where hot exhaust gases for example are fed to the heating device 35, asis illustrated in FIG. 6, the control means 33' may include a valvemeans 52 which is opened or closed to emit or restrict the flow ofexhaust gases through line 54 via line 56 to the heating means 37' whichin turn thus controls the temperature to which the secondary fuel isheated. The control means may additionally or alternatively control thequantity of liquid secondary fuel fed to the heating device 35, toensure adequate heating to cause cracking of the secondary fuel.

The apparatus 25 described with reference to FIGS. 2 to 4, is sizedideally for an average family sized motor car having a total enginecapacity of, say, up to 2 liters. For larger capacity engines, such asengines which are used industrially in lorries or the like, thedimensions of the apparatus 25 could be scaled up. Preferably though, aplurality of smaller dimensions of such apparatus 25 are provided toenable a sufficient quantity of cracked secondary fuel to be supplied tothe combustion chambers of the engine. Such plurality of apparatus mayeach contribute secondary fuel in a vapour state to the engine, directlyor via a common reservoir of vapours.

Although the invention has been described with reference to an internalcombustion engine comprising four combustion chambers, the invention maybe applied to an internal combustion engine having any number ofcombustion chambers.

Whereas the invention has been described with reference to an internalcombustion engine having combustion chambers in which there is a pistonwhich reciprocates, the invention may be applied to an engine in whichthe piston or other driven part is rotatable or otherwise movable inresponse to the ignition of fuel/air mixture in the combustion chamber.The invention may even be applied to a jet or rocket engine.

In the arrangement described in FIG. 1, the air which is fed into theinlet manifold 15 is at ambient pressure, or only a slightly raisedpressure compared with atmosphere, whereas if desired, the air could beat least partially compressed before entering the or an appropriatecombustion chamber. In this latter event, it may be necessary to providesome means to pump the cracked secondary fuel in vapour state to theinlet manifold 15.

In yet another arrangement, instead of feeding the cracked secondaryfuel in vapour state to the inlet manifold 15, this may be injecteddirectly into the combustion chamber or chambers of the engine alongwith or separately from the primary fuel.

What is claimed is:
 1. An engine comprising at least one combustionchamber in which fuel and air are ignited to produce power, deliverymeans to deliver the primary fuel to the combustion chamber, airdelivery means to provide air to the combustion chamber and includingdelivery duct means through which the air flows prior to entering thecombustion chamber, an apparatus to provide a secondary fuel to thecombustion chamber, the secondary fuel being different from the primaryfuel, characterized in that the apparatus which provides the secondaryfuel to the combustion chamber comprises a housing having therein:(a) achamber in which the secondary fuel is stored in liquid state, and, (b)a heating device into which liquid fuel may flow from the chamber, theheating device being adapted to heat the secondary fuel sufficiently tocause at least vaporization thereof, the heating device being containedwithin a sheath which is generally cylindrical and generally concentricwith the housing, the heating device including a heat exchanger intowhich the liquid secondary fuel passes from the chamber of the housingand a heating means to provide heat to the heat exchanger such that thesecondary fuel is heated therein, the heat exchanger being insulatedfrom the liquid secondary fuel in the chamber by insulation providedbetween the sheath and the heat exchanger and prior to passing into theheat exchanger, the secondary fuel, in liquid state, passes into ajacket surrounding the heating device such that the fuel is preheated,and the housing having outlet means from which the secondary fuel canpass in vapor state and there being passage means along which thesecondary fuel flow towards the combustion chamber.
 2. An engineaccording to claim 1 characterized in that the heating means comprisesan electrical heating element and temperature sensing means are providedto sense the temperature to which the secondary fuel is heated by theheating element, and to provide a signal to a remote control means whichcontrols the heating effect of the heating element.
 3. An engineaccording to claim 1 characterized in that heat generated by theinternal combustion engine is harnessed to heat the secondary fuel,wherein hot exhaust gases are fed to the heating device and the heatthereof exchanged in the heat exchanger with the secondary fuel, and acontrol means is provided which includes a valve means to control theamount of the exhaust gases and hence the heat thereof generated by theinternal combustion engine, which is fed to the heating device, thecontrol means being adapted to maintain the temperature to which thesecondary fluid is heated, to a temperature in the range 310° C. to 450°C. to crack the hydrocarbon based secondary fuel.
 4. An improvement foran engine comprising at least one combustion chamber in which fuel andair are ignited to produce power, delivery means to deliver a primaryfuel to the combustion chamber, air delivery means to provide air to thecombustion chamber and including delivery duct means through which theair flows prior to entering the combustion chamber, an apparatus toprovide a secondary fuel to the combustion chamber, the secondary fuelbeing different from the primary fuel wherein the apparatus whichprovides the secondary fuel to the combustion chamber comprises ahousing having therein (a) a chamber in which the secondary fuel isstored in liquid state, and (b) a heating device into which liquidsecondary fuel may flow from the chamber, the heating device beingadapted to heat the secondary fuel sufficiently to cause at leastvaporization thereof, the housing having outlet means from which thesecondary fuel can pass in a vapor state, and there being passage meansalong which the secondary fuel flows towards the combustion chamber, theimprovement comprising:means for limiting the degree to which thechamber can be filled with liquid secondary fuel such that the space isprovided above the liquid into which the secondary fuel in a vapor statemay pass from the heating device prior to passing out of the housing viathe outlet means, and the heating device being contained within a sheathwhich is located within the housing, the heating devices including aheat exchanger into which the liquid secondary fuel passes from thechamber of the housing and a heating means to provide heat to the heatexchanger such that the secondary fuel is heated therein.
 5. An engineaccording to claim 4, wherein the heat exchanger is insulated from theliquid secondary fuel in the chamber by insulation provided between thesheath and the heat exchanger.
 6. An engine according to claim 4,wherein prior to passing into the heat exchanger, the secondary fuel, ina liquid state, passes into a jacket surrounding the heating device suchthat the secondary fuel is preheated.
 7. An engine according to claim 5,wherein prior to passing into the heat exchanger, the secondary fuel, ina liquid state, passes into a jacket surrounding the heating device suchthat the secondary fuel is preheated.
 8. An engine according to claim 4,wherein the housing is substantially cylindrical, the housing comprisinga cylindrical side wall and top and bottom closure plates, the sheathbeing generally cylindrical and generally concentric with the housing.9. An engine according to claim 4, wherein the heating means comprisesan electrical heating element and temperature sensing means are providedto sense the temperature to which the secondary fuel is heated by theheating element, said temperature sensing means providing a signal toremote control means which controls the heating effect of the heatingelement.
 10. An engine according to claim 4, wherein heat generated bythe engine is harnessed to heat the secondary fuel, hot exhaust gasesare fed to the heating device and the heat thereof exchanged in the heatexchanger with the secondary fuel, and a control means is provided whichincludes a valve means to control the combustion engine, which is fed tothe heating device.
 11. An engine according to claim 9, wherein thecontrol means is adapted to maintain the temperature to which thesecondary fuel is heated, to a temperature in the range of 310° C. to450° C. to crack the secondary fuel.
 12. An engine according to claim10, wherein the control means is adapted to maintain the temperature towhich the secondary fuel is heated, to a temperature in the range of310° C. to 450° C. to crack the secondary fuel.
 13. An engine accordingto claim 11, wherein the secondary fuel is hydrocarbon based.
 14. Anengine according to claim 12, wherein the secondary fuel is hydrocarbonbased.
 15. An engine according to claim 4, comprising a plurality of thesecondary fuel apparatus, each secondary fuel apparatus feedingsecondary fuel in a vapor state to said at least one combustion chamberof the engine.